The invention set forth in this specification pertains to new and improved dispensing closure structures. Specifically it pertains to dispensing closure structures employing bearings and trunnions of a specialized shape and configuration as hereinafter indicated for mounting a movable part such as a spout upon a cap part.
The term or expression "dispensing closure" is currently used to designate a two or more piece closure structure which is constructed so as to include a cap or cap part either adapted to be mounted upon a conventional container, or to be formed integrally with such container and a movable part such as a spout or lid pivotally mounted on such a cap part so as to be capable of being moved between open and closed positions. These closures have normally been constructed so as to include bearing openings or cavities in the cap part having restricted entrances enabling the movable parts of such closures to be snapped in place within such bearing openings during the assembly of such closures.
In order to achieve such a manner or mode of assembly it is, of course, necessary to manufacture at least one of the parts of such a closure of a resilient material capable of temporary deformation during closure assembly. It has been commonplace to manufacture both of the parts used in such a closure of such a material. Such closures have been manufactured in tremendous numbers with both of such parts being constructed of a comparatively soft, resilient material such as low density or non-linear polyethylene. When such parts are manufactured of polyolefin material they have, of course, been manufactured by conventional injection molding techniques.
While low density polyethylene is a very effective desirable material for use in manufacturing dispensing closure structures this material is nevertheless considered undesirable in some applications. It is not considered that an understanding of the present invention requires a detailed discussion of the reasons for this. For essentially commercial type reasons at the present time it is frequently desired to manufacture dispensing closures so that one or both of the parts of such closures are formed out of a comparatively hard but yet somewhat resilient polyolefin polymer such as linear or high density polyethylene or polypropylene.
Although known types of dispensing closures have been manufactured out of such comparatively hard materials, problems have been encountered during the manufacture of closures using such materials. On occasion during the molding of the cap parts of such closures such closures have been damaged. Such damage is considered to be the result of a significant buildup of stresses and strains in cap parts adjacent to the bearing openings in such parts as such cap parts are removed from a mold and/or the parts of a mold creating such bearing openings and the entrances to them. This damage is considered to be related to the limited resiliency and flexibility of such relatively hard materials and the stress concentrations within them as they are removed from a mold and/or mold part.
Further, on occasion the cap part and/or the trunnions of the movable parts of such dispensing closures in which one or both of such parts are formed out of a comparatively hard polymer material have been damaged for substantially the same reasons. Such damage is considered to be the result of an absence or lack of sufficient resiliency and flexibility in one or both of such parts to accommodate the trunnions on the movable parts being snapped or popped into position without material being damaged.